/* ============ RESET & BASE ============ */
  *, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
  html, body {
    -webkit-tap-highlight-color: transparent;
    -webkit-touch-callout: none;
    overscroll-behavior: contain;
  }
  body {
    padding-top: env(safe-area-inset-top);
    padding-bottom: env(safe-area-inset-bottom);
    padding-left: env(safe-area-inset-left);
    padding-right: env(safe-area-inset-right);
  }
  /* Allow text selection where it matters (code blocks, inputs) */
  .code-block, .code-input, input, textarea { -webkit-touch-callout: default; }
  :root {
    --cream: #FFF8EE;
    --cream-dark: #F2E5CE;
    --card: #FFFFFF;
    --line: #EDE0CB;

    --text: #3C2A1E;
    --text-soft: #8B7965;
    --text-faint: #BDAA94;

    --java: #FF8C42;
    --java-dark: #C4621E;
    --java-deep: #8B5A3C;
    --espresso: #4A2511;

    --green: #58CC02;
    --green-dark: #46A302;
    --green-soft: #D7FFB8;

    --red: #FF4B4B;
    --red-dark: #D33;
    --red-soft: #FFDFE0;

    --gold: #FFC800;
    --gold-dark: #E0AC00;

    --streak: #FF9600;
    --streak-dark: #E08200;

    --blue: #1CB0F6;
    --blue-dark: #1899D6;

    --purple: #CE82FF;
    --purple-dark: #A560D0;

    --pink: #FF86B0;
    --pink-dark: #D6688D;

    --gray: #E5E5E5;
    --gray-dark: #BFBFBF;

    --shadow-press: 0 4px 0 0;
  }

  html, body {
    height: 100%;
    -webkit-tap-highlight-color: transparent;
    -webkit-font-smoothing: antialiased;
    text-rendering: optimizeLegibility;
  }
  body {
    font-family: 'Nunito', system-ui, sans-serif;
    background: var(--cream);
    color: var(--text);
    font-weight: 700;
    overflow-x: hidden;
  }
  button { font-family: inherit; cursor: pointer; border: none; background: none; color: inherit; }
  code, .mono { font-family: 'JetBrains Mono', ui-monospace, Menlo, monospace; }

  /* ============ APP SHELL ============ */
  #app {
    max-width: 480px;
    min-height: 100vh;
    margin: 0 auto;
    background: var(--cream);
    position: relative;
    overflow: hidden;
  }
  @media (min-width: 700px) {
    body {
      background:
        radial-gradient(circle at 10% 20%, #FFE9D2 0%, transparent 30%),
        radial-gradient(circle at 90% 80%, #FFD9B8 0%, transparent 30%),
        var(--cream);
    }
    #app {
      box-shadow: 0 0 60px rgba(140, 80, 30, 0.12);
      border-radius: 0;
      min-height: 100vh;
    }
  }

  /* ============ TOPBAR ============ */
  .topbar {
    position: sticky; top: 0; z-index: 30;
    background: var(--cream);
    padding: 14px 16px 12px;
    display: flex; align-items: center; gap: 10px;
    border-bottom: 1px solid var(--line);
  }
  .stat {
    display: flex; align-items: center; gap: 5px;
    font-weight: 800; font-size: 16px;
    padding: 4px 8px; border-radius: 10px;
  }
  .stat svg { width: 22px; height: 22px; flex: none; }
  .stat-streak { color: var(--streak); }
  .stat-streak.cold { color: var(--text-faint); }
  .stat-hearts { color: var(--red); }
  .stat-xp { color: var(--gold-dark); }
  .topbar-spacer { flex: 1; }
  .icon-btn {
    width: 38px; height: 38px; border-radius: 12px;
    display: grid; place-items: center;
    color: var(--text-soft);
  }
  .icon-btn:hover { background: var(--cream-dark); }
  .icon-btn svg { width: 22px; height: 22px; }

  /* ============ TYPOGRAPHY ============ */
  h1, h2, h3 { font-family: 'Fredoka', 'Nunito', sans-serif; font-weight: 700; line-height: 1.15; }
  h1 { font-size: 28px; }
  h2 { font-size: 22px; }
  h3 { font-size: 18px; }
  p { line-height: 1.45; }

  /* ============ BUTTONS (Duolingo chunky press) ============ */
  .btn {
    display: inline-flex; align-items: center; justify-content: center;
    gap: 8px;
    border-radius: 16px;
    padding: 14px 20px;
    font-family: 'Nunito', sans-serif;
    font-weight: 900;
    font-size: 15px;
    letter-spacing: 0.6px;
    text-transform: uppercase;
    transition: filter 0.1s, transform 0.06s, box-shadow 0.06s;
    user-select: none;
    border: 2px solid transparent;
    box-shadow: 0 4px 0 0 var(--btn-shadow, transparent);
    background: var(--btn-bg, var(--green));
    color: var(--btn-fg, white);
    border-color: var(--btn-bg, var(--green));
    min-height: 50px;
  }
  .btn:active:not(:disabled) {
    transform: translateY(2px);
    box-shadow: 0 2px 0 0 var(--btn-shadow, transparent);
  }
  .btn:disabled {
    --btn-bg: #E5E5E5;
    --btn-fg: #AFAFAF;
    --btn-shadow: #BFBFBF;
    cursor: not-allowed;
    box-shadow: 0 2px 0 0 var(--btn-shadow);
  }
  .btn-primary { --btn-bg: var(--green); --btn-shadow: var(--green-dark); }
  .btn-danger { --btn-bg: var(--red); --btn-shadow: var(--red-dark); }
  .btn-java { --btn-bg: var(--java); --btn-shadow: var(--java-dark); }
  .btn-ghost {
    --btn-bg: var(--card);
    --btn-fg: var(--text-soft);
    --btn-shadow: var(--line);
    border-color: var(--line);
  }
  .btn-block { width: 100%; }
  .btn-lg { padding: 18px 24px; font-size: 16px; min-height: 58px; }
  .btn:focus-visible { outline: 3px solid #FFC800; outline-offset: 2px; }

  /* ============ SCREEN BASE ============ */
  .screen {
    padding: 20px 16px 100px;
    animation: fade 0.25s ease;
  }
  @keyframes fade { from { opacity: 0; transform: translateY(6px);} to { opacity: 1; transform: none;} }

  /* ============ MASCOT ============ */
  .mascot {
    width: 140px; height: 140px;
    display: block;
    transition: transform 0.3s cubic-bezier(.5,1.7,.5,1);
  }
  .mascot-bob { animation: bob 2.4s ease-in-out infinite; }
  @keyframes bob {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-4px); }
  }
  .mascot.celebrate { animation: celebrate 0.8s ease; }
  @keyframes celebrate {
    0%, 100% { transform: rotate(0); }
    25% { transform: rotate(-8deg) scale(1.05); }
    50% { transform: rotate(0) scale(1.1); }
    75% { transform: rotate(8deg) scale(1.05); }
  }
  .mascot.shake { animation: shake 0.4s ease; }
  @keyframes shake {
    0%, 100% { transform: translateX(0); }
    20% { transform: translateX(-6px) rotate(-3deg); }
    40% { transform: translateX(6px) rotate(3deg); }
    60% { transform: translateX(-4px) rotate(-2deg); }
    80% { transform: translateX(4px) rotate(2deg); }
  }
  .mascot-row {
    display: flex; align-items: center; gap: 10px;
    margin: 16px 0;
  }
  .speech {
    flex: 1;
    background: var(--card);
    border: 2px solid var(--line);
    border-radius: 16px;
    padding: 14px 16px;
    font-weight: 700;
    font-size: 15px;
    line-height: 1.45;
    position: relative;
  }
  .speech::before {
    content: ''; position: absolute;
    left: -10px; top: 26px;
    width: 14px; height: 14px;
    background: var(--card);
    border-left: 2px solid var(--line);
    border-bottom: 2px solid var(--line);
    transform: rotate(45deg);
  }

  /* ============ WELCOME SCREEN ============ */
  .welcome {
    text-align: center;
    padding: 40px 20px 100px;
    min-height: 100vh;
    display: flex; flex-direction: column; align-items: center;
  }
  .welcome .mascot { width: 200px; height: 200px; margin: 30px 0 16px; }
  .welcome h1 {
    font-size: 36px; color: var(--java-dark); margin-bottom: 8px;
  }
  .welcome .tagline {
    color: var(--text-soft); margin-bottom: 30px; font-size: 16px;
  }
  .welcome .actions { width: 100%; max-width: 320px; display: flex; flex-direction: column; gap: 12px; margin-top: auto; }

  /* ============ PATH SCREEN ============ */
  .unit-banner {
    background: var(--unit-color, var(--java));
    color: white;
    border-radius: 18px;
    padding: 16px 20px;
    display: flex; align-items: center; gap: 14px;
    margin: 16px 0 4px;
    box-shadow: 0 4px 0 0 var(--unit-shadow, var(--java-dark));
  }
  .unit-banner-info { flex: 1; min-width: 0; }
  .unit-banner-eyebrow {
    font-size: 11px; letter-spacing: 1.2px; opacity: 0.85;
    text-transform: uppercase; font-weight: 800;
  }
  .unit-banner-title { font-family: 'Fredoka', sans-serif; font-size: 20px; }
  .unit-banner-icon {
    width: 56px; height: 56px;
    background: rgba(255,255,255,0.18);
    border-radius: 14px; display: grid; place-items: center;
    flex: none;
  }
  .unit-banner-icon svg { width: 32px; height: 32px; color: white; }

  .lesson-path {
    display: grid; grid-template-columns: 1fr 1fr 1fr;
    gap: 0; padding: 22px 0 30px;
    position: relative;
  }
  .lesson-node {
    position: relative; z-index: 1;
    display: flex; flex-direction: column; align-items: center;
    margin: 0 auto;
    gap: 4px;
    padding: 4px 0;
  }
  .lesson-node-row-1 { grid-column: 2; }
  .lesson-node-row-2 { grid-column: 3; transform: translateY(-6px); }
  .lesson-node-row-3 { grid-column: 2; transform: translateY(-12px); }
  .lesson-node-row-4 { grid-column: 1; transform: translateY(-18px); }
  .lesson-node-row-5 { grid-column: 2; transform: translateY(-24px); }
  .lesson-node-row-6 { grid-column: 3; transform: translateY(-30px); }

  .lesson-bubble {
    width: 78px; height: 78px;
    border-radius: 50%;
    display: grid; place-items: center;
    background: var(--node-bg, var(--unit-color));
    color: white;
    box-shadow: 0 6px 0 0 var(--node-shadow, var(--unit-shadow));
    border: 4px solid white;
    transition: transform 0.06s, box-shadow 0.06s;
    position: relative;
  }
  .lesson-bubble svg { width: 36px; height: 36px; }
  .lesson-node-current .lesson-bubble {
    animation: pulse 1.6s ease-in-out infinite;
  }
  @keyframes pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.07); }
  }
  .lesson-node[data-locked="true"] .lesson-bubble {
    --node-bg: #E5E5E5; --node-shadow: #BFBFBF;
    color: #AFAFAF;
    cursor: not-allowed;
  }
  .lesson-node[data-completed="true"] .lesson-bubble {
    --node-bg: var(--gold);
    --node-shadow: var(--gold-dark);
    color: white;
  }
  .lesson-node:not([data-locked="true"]) .lesson-bubble:active {
    transform: translateY(2px);
    box-shadow: 0 4px 0 0 var(--node-shadow);
  }
  .lesson-label {
    font-size: 12px; color: var(--text-soft);
    font-weight: 800; max-width: 100px; text-align: center;
    line-height: 1.2;
  }

  .start-tag {
    position: absolute; top: -34px; left: 50%; transform: translateX(-50%);
    background: white;
    border: 2px solid var(--line);
    color: var(--unit-color);
    padding: 6px 12px; border-radius: 14px;
    font-size: 12px; font-weight: 900;
    letter-spacing: 0.4px;
    box-shadow: 0 2px 0 0 var(--line);
    white-space: nowrap;
  }
  .start-tag::after {
    content: ''; position: absolute;
    left: 50%; bottom: -7px; transform: translateX(-50%) rotate(45deg);
    width: 10px; height: 10px;
    background: white;
    border-right: 2px solid var(--line);
    border-bottom: 2px solid var(--line);
  }

  /* ============ LESSON HEADER ============ */
  .lesson-header {
    display: flex; align-items: center; gap: 14px;
    padding: 14px 16px;
    border-bottom: none;
    background: var(--cream);
    position: sticky; top: 0; z-index: 30;
  }
  .progress-bar {
    flex: 1;
    height: 14px;
    background: var(--cream-dark);
    border-radius: 8px;
    overflow: hidden;
    position: relative;
  }
  .progress-bar-fill {
    height: 100%;
    background: var(--green);
    border-radius: 8px;
    width: 0%;
    transition: width 0.4s cubic-bezier(.4,1.5,.4,1);
    position: relative;
  }
  .progress-bar-fill::after {
    content: ''; position: absolute;
    top: 2px; left: 6px; right: 6px; height: 4px;
    background: rgba(255,255,255,0.5);
    border-radius: 4px;
  }

  /* ============ LESSON BODY ============ */
  .lesson-body {
    padding: 8px 18px 20px;
    min-height: calc(100vh - 220px);
    display: flex; flex-direction: column;
  }
  .question-prompt {
    font-family: 'Fredoka', sans-serif;
    font-size: 22px;
    font-weight: 600;
    margin: 8px 0 18px;
    color: var(--text);
    line-height: 1.25;
  }
  .code-block {
    background: #FFFCF5;
    border: 2px solid var(--line);
    border-radius: 14px;
    padding: 14px 16px;
    margin: 6px 0 18px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 14px;
    line-height: 1.6;
    color: var(--text);
    white-space: pre-wrap;
    word-break: break-word;
  }

  /* ============ CODE INPUT (type questions) ============ */
  .code-input-wrap { margin: 8px 0 18px; }
  .code-input {
    width: 100%;
    background: #FFFCF5;
    border: 2px solid var(--line);
    border-radius: 14px;
    padding: 14px 16px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 15px;
    line-height: 1.6;
    color: var(--text);
    resize: vertical;
    min-height: 84px;
    transition: border-color 0.15s, box-shadow 0.15s;
    outline: none;
    -webkit-text-size-adjust: 100%;
  }
  .code-input:focus {
    border-color: var(--orange);
    box-shadow: 0 0 0 4px rgba(255, 140, 66, 0.15);
  }
  .code-input.correct { border-color: var(--green); background: #F0FBE3; }
  .code-input.wrong { border-color: var(--red); background: #FFF1F0; }
  .code-hint {
    display: flex;
    align-items: center;
    gap: 6px;
    font-family: 'Nunito', sans-serif;
    font-size: 13px;
    color: var(--muted);
    margin-top: 8px;
    font-weight: 700;
  }
  .code-hint .mono { font-family: 'JetBrains Mono', monospace; font-size: 12.5px; background: var(--cream-dark); padding: 1px 6px; border-radius: 5px; color: var(--text); }

  /* ============ INTRO CARD ============ */
  .intro-card {
    text-align: left;
  }
  .intro-card .mascot { margin: 0 auto 16px; }
  .intro-card h2 {
    text-align: center;
    color: var(--java-dark);
    margin-bottom: 14px;
  }
  .intro-card .intro-content {
    background: var(--card);
    border: 2px solid var(--line);
    border-radius: 16px;
    padding: 16px 18px;
    line-height: 1.55;
    font-weight: 600;
    font-size: 15px;
    color: var(--text);
  }
  .intro-card .intro-content p { margin-bottom: 10px; }
  .intro-card .intro-content p:last-child { margin-bottom: 0; }
  .intro-card .intro-content code {
    background: var(--cream-dark);
    padding: 2px 6px; border-radius: 6px;
    font-size: 13px; font-weight: 700;
    color: var(--java-dark);
  }
  .intro-card .intro-content pre {
    background: #FFFCF5;
    border: 1.5px solid var(--line);
    border-radius: 10px;
    padding: 10px 12px;
    margin: 8px 0;
    font-family: 'JetBrains Mono', monospace;
    font-size: 13px;
    line-height: 1.55;
    color: var(--text);
    white-space: pre-wrap;
    word-break: break-word;
  }

  /* ============ MULTIPLE CHOICE ============ */
  .options { display: flex; flex-direction: column; gap: 10px; }
  .option {
    display: flex; align-items: center; gap: 12px;
    padding: 14px 16px;
    border-radius: 14px;
    background: var(--card);
    border: 2px solid var(--line);
    box-shadow: 0 3px 0 0 var(--line);
    font-weight: 800;
    font-size: 15px;
    text-align: left;
    cursor: pointer;
    transition: transform 0.06s, box-shadow 0.06s;
    color: var(--text);
    line-height: 1.35;
  }
  .option .opt-key {
    width: 28px; height: 28px;
    border: 2px solid var(--line);
    border-radius: 8px;
    display: grid; place-items: center;
    font-family: 'Nunito';
    font-size: 13px;
    color: var(--text-soft);
    flex: none;
    background: white;
  }
  .option:active { transform: translateY(2px); box-shadow: 0 1px 0 0 var(--line); }
  .option.selected {
    border-color: var(--blue);
    background: #E5F8FF;
    color: var(--blue-dark);
    box-shadow: 0 3px 0 0 #B7E4F4;
  }
  .option.selected .opt-key { border-color: var(--blue); color: var(--blue-dark); }
  .option.correct {
    border-color: var(--green-dark);
    background: var(--green-soft);
    color: var(--green-dark);
    box-shadow: 0 3px 0 0 var(--green-dark);
  }
  .option.correct .opt-key { border-color: var(--green-dark); color: var(--green-dark); background: white; }
  .option.wrong {
    border-color: var(--red-dark);
    background: var(--red-soft);
    color: var(--red-dark);
    box-shadow: 0 3px 0 0 var(--red-dark);
  }
  .option.wrong .opt-key { border-color: var(--red-dark); color: var(--red-dark); background: white; }
  .option code, .option .mono {
    font-family: 'JetBrains Mono', monospace;
    font-size: 13.5px;
    font-weight: 700;
  }

  /* ============ BUILD CODE (tap tiles) ============ */
  .build-area {
    min-height: 64px;
    background: var(--card);
    border-radius: 14px;
    border: 2px dashed var(--line);
    padding: 12px;
    display: flex; flex-wrap: wrap; gap: 8px;
    align-content: flex-start;
    margin-bottom: 14px;
    line-height: 1.4;
  }
  .build-area:empty::before {
    content: 'Tap tiles below…';
    color: var(--text-faint);
    font-size: 14px;
    font-style: italic;
    align-self: center;
  }
  .tile-pool {
    background: rgba(0,0,0,0.025);
    border-radius: 14px;
    padding: 12px;
    display: flex; flex-wrap: wrap; gap: 8px;
    min-height: 64px;
    align-content: flex-start;
  }
  .tile {
    background: var(--card);
    border: 2px solid var(--line);
    border-radius: 10px;
    padding: 9px 12px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 14px;
    font-weight: 700;
    color: var(--text);
    box-shadow: 0 2px 0 0 var(--line);
    transition: transform 0.06s, box-shadow 0.06s, opacity 0.15s;
    cursor: pointer;
    user-select: none;
  }
  .tile:active { transform: translateY(2px); box-shadow: 0 0 0 0 var(--line); }
  .tile.used {
    background: var(--cream-dark);
    color: var(--text-faint);
    border-color: var(--line);
    box-shadow: none;
    cursor: default;
  }

  /* ============ FILL BLANK ============ */
  .fb-prompt code {
    background: var(--cream-dark);
    padding: 2px 6px; border-radius: 6px;
    font-size: 13.5px;
  }
  .fb-blank {
    display: inline-block;
    min-width: 60px;
    padding: 1px 8px;
    background: var(--card);
    border-bottom: 3px solid var(--text-soft);
    margin: 0 2px;
    color: var(--blue-dark);
    font-weight: 800;
    text-align: center;
  }
  .fb-blank.filled { background: #E5F8FF; }

  /* ============ FEEDBACK BAR ============ */
  .feedback {
    position: fixed;
    bottom: 0; left: 50%;
    transform: translateX(-50%);
    width: 100%; max-width: 480px;
    background: var(--fb-bg, var(--green-soft));
    border-top: 2px solid var(--fb-border, var(--green-dark));
    padding: 16px 18px 20px;
    z-index: 50;
    animation: slideUp 0.3s cubic-bezier(.4,1.5,.4,1);
  }
  @keyframes slideUp { from { transform: translate(-50%, 100%); } to { transform: translate(-50%, 0); } }
  .feedback h3 {
    font-family: 'Fredoka', sans-serif;
    color: var(--fb-color, var(--green-dark));
    margin-bottom: 4px;
    font-size: 22px;
  }
  .feedback p {
    color: var(--fb-color-soft, #4A8002);
    font-weight: 700;
    font-size: 14px;
    line-height: 1.45;
    margin-bottom: 12px;
  }
  .feedback p code {
    font-family: 'JetBrains Mono', monospace;
    background: rgba(255,255,255,0.6);
    padding: 1px 5px;
    border-radius: 5px;
    font-size: 12.5px;
  }
  .feedback.wrong {
    --fb-bg: var(--red-soft);
    --fb-border: var(--red-dark);
    --fb-color: var(--red-dark);
    --fb-color-soft: #B22;
  }
  .check-bar {
    position: fixed;
    bottom: 0; left: 50%;
    transform: translateX(-50%);
    width: 100%; max-width: 480px;
    background: var(--cream);
    border-top: 1px solid var(--line);
    padding: 12px 16px 16px;
    z-index: 49;
  }

  /* ============ HEART LOSS ANIMATION ============ */
  .heart-pop {
    position: absolute; pointer-events: none;
    color: var(--red); font-size: 28px;
    animation: heartFly 0.9s ease forwards;
  }
  @keyframes heartFly {
    0% { transform: scale(1); opacity: 1; }
    100% { transform: scale(1.6) translateY(-30px); opacity: 0; }
  }

  /* ============ COMPLETE SCREEN ============ */
  .complete-screen {
    text-align: center;
    padding: 40px 20px 100px;
    min-height: 100vh;
    display: flex; flex-direction: column; align-items: center;
  }
  .complete-screen .mascot { width: 180px; height: 180px; margin-bottom: 16px; }
  .complete-screen h1 {
    font-size: 32px; color: var(--java-dark);
    margin-bottom: 8px;
  }
  .complete-screen .reward-row {
    display: grid; grid-template-columns: 1fr 1fr 1fr;
    gap: 10px; margin: 26px 0;
    width: 100%;
  }
  .reward-card {
    background: var(--card);
    border: 2px solid var(--line);
    border-radius: 14px;
    padding: 12px 8px;
    box-shadow: 0 3px 0 0 var(--line);
    text-align: center;
  }
  .reward-card .reward-label {
    font-size: 11px;
    text-transform: uppercase;
    letter-spacing: 0.6px;
    color: var(--text-soft);
    margin-bottom: 6px;
    font-weight: 800;
  }
  .reward-card .reward-value {
    font-family: 'Fredoka', sans-serif;
    font-size: 22px;
    font-weight: 700;
    color: var(--reward-color, var(--text));
  }
  .reward-card svg { width: 28px; height: 28px; margin-bottom: 4px; }
  .reward-xp .reward-value { color: var(--gold-dark); }
  .reward-streak .reward-value { color: var(--streak); }
  .reward-time .reward-value { color: var(--blue-dark); }

  /* ============ CONFETTI ============ */
  .confetti {
    position: fixed; top: -20px; width: 10px; height: 14px;
    pointer-events: none;
    animation: fall 2.5s linear forwards;
  }
  @keyframes fall {
    0% { transform: translateY(0) rotate(0); opacity: 1; }
    100% { transform: translateY(110vh) rotate(720deg); opacity: 0.4; }
  }

  /* ============ MODAL ============ */
  .modal-bg {
    position: fixed; inset: 0;
    background: rgba(60,42,30,0.5);
    display: grid; place-items: center;
    z-index: 100;
    padding: 20px;
    animation: fade 0.2s ease;
  }
  .modal {
    background: var(--card);
    border-radius: 20px;
    padding: 26px 22px 22px;
    text-align: center;
    max-width: 380px; width: 100%;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
  }
  .modal h2 { color: var(--java-dark); margin-bottom: 8px; }
  .modal p { color: var(--text-soft); font-weight: 700; margin-bottom: 18px; line-height: 1.45; }
  .modal-actions { display: flex; flex-direction: column; gap: 10px; }

  /* ============ EMPTY STATE / NO HEARTS ============ */
  .nohearts-screen {
    text-align: center; padding: 60px 24px 100px;
    min-height: 100vh;
    display: flex; flex-direction: column; align-items: center;
  }
  .nohearts-screen .mascot { width: 160px; height: 160px; margin-bottom: 12px; }
  .nohearts-screen h1 { color: var(--red-dark); margin-bottom: 10px; }
  .nohearts-screen p { color: var(--text-soft); margin-bottom: 28px; line-height: 1.4; }

  /* ============ DEBUG MENU ============ */
  .debug-toast {
    position: fixed; bottom: 20px; left: 50%;
    transform: translateX(-50%);
    background: var(--text); color: white;
    padding: 10px 16px; border-radius: 12px;
    font-size: 13px;
    z-index: 200;
    animation: fade 0.2s ease;
  }

  /* ============ LANGUAGE SWITCHER ============ */
  .lang-tabs {
    display: flex; gap: 8px;
    margin: 4px 0 8px;
  }
  .lang-tab {
    flex: 1;
    padding: 10px 8px;
    border-radius: 14px;
    border: 2px solid var(--line);
    background: var(--card);
    font-family: 'Nunito', sans-serif;
    font-weight: 900;
    font-size: 14px;
    cursor: pointer;
    color: var(--text-soft);
    box-shadow: 0 3px 0 0 var(--line);
    transition: transform 0.06s, box-shadow 0.06s;
  }
  .lang-tab:active { transform: translateY(2px); box-shadow: 0 1px 0 0 var(--line); }
  .lang-tab.active[data-lang="java"] {
    background: var(--java); border-color: var(--java-dark);
    color: white; box-shadow: 0 3px 0 0 var(--java-dark);
  }
  .lang-tab.active[data-lang="python"] {
    background: #3776AB; border-color: #2B5E8E;
    color: white; box-shadow: 0 3px 0 0 #2B5E8E;
  }

  /* AI hint shown in feedback bar */
  .ai-hint {
    background: rgba(255,255,255,0.5);
    border-radius: 8px;
    padding: 8px 10px;
    margin-top: 6px;
    font-size: 13px;
    line-height: 1.45;
    font-weight: 700;
  }